ci(root): add Codecov to workflow build.yml

[remarkablemark]

https://github.com/codecov/codecov-action

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (master@fc26150). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             master       #21   +/-   ##
==========================================
  Coverage          ?   100.00%           
==========================================
  Files             ?         4           
  Lines             ?        32           
  Branches          ?         2           
==========================================
  Hits              ?        32           
  Misses            ?         0           
  Partials          ?         0           

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